The importance of biogenic amines in neurotransmission, metabolism, and in control of various physiological processes has spurred intense interest in the development of precise and sensitive methods for the quantitation of these amines and their metabolites present in cerebrospinal fluid, plasma and urine. We have developed precise, operationally simple procedures for the analyses of certain of these substances based on HPLC separation using highly sensitive electrochemical detection, coupled with the use of internal standards for accurate quantitation. The utility of the approach has been extended greatly by selective and efficient acylation of the endogenous amines which permits ready isolation from the biological sample. Use of an electroactive acylating reagent further extends this approach to the accurate detection of amines which, themselves, are not amenable to electrochemical detection (e.g., histamine and phenethylamine).